As should be apparent to those skilled in the construction of aircraft from non-metallic materials, there are circumstances where it becomes necessary to position an insert into an opening or hole in the material. The insert may be a solid plug or a bushing, among other possibilities.
In one contemplated example, it may be necessary to plug a hole drilled in the composite material incorrectly, such as of a wrong size or at an incorrect location.
In another contemplated example, it may be desirable to insert a bushing into an opening to accommodate a shaft therein. The bushing may provide a suitable location for a rotating shaft, for example.
As should be apparent to those skilled in the art, composite materials present a unique challenge when inserting a plug or bushing therein. Specifically, composite materials that are commonly used in the construction of aircraft typically are formed from multiple plies of woven carbon fiber fabric that are suspended in a resin matrix.
When inserting a plug or bushing into the composite material, care must be taken to avoid delamination of the composite material. Too much pressure on the composite material also may result in cracking and/or damage to the composite material.
In addition, it is important for the plug or bushing to be fitted into an opening with a sufficient interference to discourage removal or dislodgement of the plug and/or bushing from the opening. If the interference is insufficient, the bushing or plug might be inadvertently removed from the opening. If the interference it too tight, the pressure applied by the plug and/or bushing on the inner diameter of the opening might be so great to cause the composite material to crack or otherwise become damaged.
An additional challenge when inserting plugs or bushings into a composite material is that corrosion issues may arise. Specifically, the material from which the insert is made may not be compatible with the materials from which the composite material is made. In some instances of incompatibility, the insert may react chemically and/or electrochemically with the composite material, resulting in corrosion of one or both of the materials.
Also, when positioning an insert in a composite material, there are limitations on the handling of the composite material. Specifically, it is imprudent to heat the composite material before inserting the plug or bushing therein. Heating of the composite material may affect the physical properties of the composite material.
Separately, the coefficient of thermal expansion (“CTE”) for the insert should be selected so that the CTE for the insert is compatible with the CTE for the composite material. If the CTEs for the two materials are incompatible, there is a possibility that one or both of the insert and/or the composite material may experience micro-cracking.
The prior art does not provide a suitable solution to one or more of the difficulties enumerated above.
Accordingly, an improved method for inserting a plug or bushing into an opening in a composite material is desirable.